The price per gallon of gasoline changes often. Most drivers pay close attention to those changes. Find the percent change in price for each of these cases.

a) increase from $4.00 per gallon to $4.20

b) increase from $3.00 per gallon to $3.75

c) decrease from $3.75 per gallon to $3.00

A) The amount of change is. 20 (20 cents) so we need to find what percent of $4.00 is. 20 ...

4 * x =.20

x =.20/4 =.05

Multiply by 100 (move decimal 2 places to the right) to change decimal to percent.

.05 = 5% increase

b) The increase is. 75. What percent of 3.00 is. 75

3 * x =.75

x =.75/3

x =.25 x 100 = 25% increase

c) The amount of change is. 75 but this time we are going from 3.75 to 3.00 so we find out what percent. 75 is of 3.75.

3.75 * x =.75

x =.75/3.75

x =.20 x 100 = 20% decrease